1. Field of the Invention
This invention relates generally to protective guards for railroad crossings and more particularly to lift-type or rocking-type gate mechanisms for use at railroad crossings where the gate mechanism is counterbalanced with external weights to enable a smaller or less powerful motor to be used to operate such gate.
2. Prior Art
Railroad crossings are guarded with three principal types of protective apparatus to prevent vehicles moving on intersecting roads from being struck by passing trains. Such protective apparatus comprises primarily marker signs, flashing and frequently audible signals and/or automatic gates that, when lowered, extend over or across the road to block access to the railroad tracks at the crossing by vehicles. In prior years, there were also watchmen at heavily traveled railroad crossings, whose job it was to direct traffic to stop by means of hand-held signs or signals or frequently by the use of manually-operated, vertically or horizontally swinging gates. Manually-operated, vertically swinging gates were largely hand cranked and provided with a large gear ratio which seriously restricted the speed with which a gate could be deployed or operated. With the development of automatic motor-operated equipment to activate the gate mechanisms, the more costly watchmen or gatemen have almost universally been replaced by automatic gate apparatus.
In hand-cranked gates, the blocking arm of the gate was customarily counterbalanced by a counterweight or, more usually, multiple counterweights supported on the opposite end of the gate arm to counterbalance the weight structure and relieve as much weight or stress as possible from the gateman. With the disappearance of the gateman, such counterweights have become even more important, since it is desirable to use as small a motor as possible to efficiently raise and lower the gate, while at the same time pivoting the gate as rapidly or quickly as possible consonant with not moving so fast as to endanger pedestrians and vehicles. Pedestrians and vehicles should preferably not, of course, be struck by a descending gate; nor should a gate be struck by a rapidly moving vehicle. Rapid operation of the gate requires that the speed of the customary electric motor powering the gate should not be reduced so drastically by gearing to obtain effective gate operating power that the gate will not operate sufficiently quickly to provide an effective barrier. Counterbalancing of the gate, therefore, becomes even more important for automatic gates in order that the motor operating the gate has as little effective weight to move as possible. A perfectly, or near perfectly, balanced gate may require practically no power at all to swing up or down at a reasonable speed. Customarily, counterweights for gates have comprised separate weights which can be applied or removed as necessary. The weights are quite frequently rectangular metal plates of different sizes and weight attached or clamped to the gate structure by some arrangement that allows the weights to be reasonably frequently moved longitudinally on the gate structure to adjust their counterbalancing effect as well as to allow the weights to be interchanged with other weights to make gross adjustments in counterbalancing. Minor adjustments are usually made by moving the longitudinal position of the weight on the gate structure, while gross adjustments may be made by interchanging the weights. Typical modern counterweight arrangements for railway crossing gates are shown in the following U.S. Patents:
U.S. Pat. No. 1,911,405 to Taylor et al. (1933) PA1 U.S. Pat. No. 2,598,196 to Staley (1952) PA1 U.S. Pat. No. 4,067,523 to Kenney et al. (1978) PA1 U.S. Pat. No. 4,090,685 to Pappas (1978)
Each of the above patents shows a gate structure with a groove in the rear gate casing or arm into which a bolt-type fastening may be inserted to clamp a counter weight or a series of counterweights in place. The Taylor et al. patent actually supports the weights on a special bracket that is adjustably clamped or held in place by the tightening of the bolt-type fastenings and the other three patents disclose the use of counterweights supported or held directly upon bolts extending through a slot in the casing of the gate. Such slot provides a channel along which the threaded fastenings or bolts may be moved when loosened to adjust the counterweights and supporting threaded fastenings along the slot in order to provide various effective lever arm configurations with respect to the effective weight of the counterweight applied to balance the weight of the gate arm. The weight of the counterweight in the Staley patent is arranged to be adjustable along a slot disposed more or less transverse to the gate arm to primarily adjust the force with which the gate is held aloft when in an upraised position. The relative counterbalancing of such arrangement is, however, relatively less adjustable when the gate is lowered. The other three listed patents disclose adjustment slots that are disposed essentially in line with the longitudinal extent of the gate arm itself. The arrangement of the counterweights shown in the U.S. Pat. Nos. 4,067,523 and 4,090,085 patents to Kenney et al. and Pappas respectively, show essentially the present state of the art of counterweight adjustment, although such patents were issued more than twenty years ago. The principal alteration in the modern counterweight systems is that the weight may be held by a single threaded member more frequently than by two as is more typically shown in most of the older apparatus.
While the arrangement shown in the Kenney et al. and Pappas patents is quite effective in providing an adjustable counterweight arrangement that, once it has been correctly adjusted, is very effective in balancing the gate arm so it can be moved quickly and economically with a minimum of power, it is relatively difficult to adjust the counterweights themselves, since such counterweights are not only quite heavy, but also awkward to handle. Since the gate arm is itself relatively heavy, the counterbalancing weights are also by necessity heavy, at least if a reasonable length counterweight arm is to be used. Consequently, maintenance personnel must not only loosen the fastenings holding the counterweights in place, but must support the heavy counterweights until they are repositioned and resecured. Since the counterweights are, furthermore, usually adjusted with the gate in a raised position to avoid interfering with traffic, frequently the gate structure itself must be supported while the counterweights are manhandled into position. This is both a time-consuming operation and fraught with opportunities for injury of the adjustment personnel ranging from hernias, strained backs, pulled tendons and the like, to crushed toes and fingers as well as other injuries too numerous to list. Furthermore, since the adjustment of the counterweights is heavy work, usually at least two maintenance workers are assigned to the job and frequently half a day or more is expended in adjusting one gate or set of gates. Furthermore, since adjusting the gate counterweights frequently takes a considerable time, the crossing normally protected may be partially unprotected during the adjustment operation. There is, therefore, a definite need for a method or apparatus or both that will facilitate adjustment of the counterweights on a gate structure.